The most common and most likely answer to this crossword clue is the 14 letter word TREASURE-TROVE
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More clues leading to the result TREASURE-TROVE
Buddy explains!

The straight part
We know that "valuable find" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case valuable find = treasure-trove.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TREASURE-TROVE mean?
TREASURE-TROVE noun- A hidden treasure, subsequently discovered.
- A valuable discovery.
- Precious metal objects that were buried or concealed by an unknown owner.
- A place where many things of value can be found.